Nowadays, receiving apparatuses capable of receiving a radio signal transmitted from a satellite are mounted on movable bodies such as vehicles and mobile phones. According to GPS (Global Positioning System) positioning, the position of a movable body on which such a receiving apparatus is mounted can be estimated. Position estimation technology using such a receiving apparatus is an important common fundamental technology in a variety of fields such as navigation, security, and entertainment. However, position estimation technology based on GPS positioning needs a long time to achieve synchronization acquisition during activation and it is difficult to use the technology indoors or underground where a radio signal from a satellite is not receivable.
Patent Document 1 discloses a technology in which PHS (Personal Handyphone System) measures signal strength of a signal transmitted from a base station and estimates the position of the local apparatus based on the measured signal strength. More specifically, the base station of PHS is installed by a communication operator and thus, the installation position thereof is normally known. Therefore, if PHS measures signal strengths of signals transmitted from three base stations or more and estimates the distance between each base station and the local apparatus based on the measured signal strength, the position of the local apparatus can be estimated on the principle of triangulation using the installation position of each base station as a reference.
Also, position estimation technology in which a communication apparatus that performs radio communication with a base station (access point) of wireless LAN (Local Area Network) measures signal strength of a signal transmitted from the base station and an information management apparatus that can communicate with the communication apparatus estimates the position of the communication apparatus based on the signal strength can be considered. For example, the base station of wireless LAN transmits a beacon for signaling the presence of the base station of wireless LAN to surroundings thereof in a constant period (for example, five times/sec). The communication apparatus transmits the signal strength of such a beacon to the information management apparatus and the information management apparatus can estimate the position of the communication apparatus based on the signal strength and the position of the base station of wireless LAN registered in advance. According to the position estimation technology, base stations of wireless LAN are also installed indoors or underground and thus, an indoor or underground position can also be estimated, which is difficult to achieve according to the position estimation technology based on GPS positioning. That is, if base station information indicating the positions of base stations of wireless LAN installed around the communication apparatus is registered with the information management apparatus, the position estimation technology can be considered to be a technology superior in convenience and simplicity.